This invention relates to the need to improve refrigeration systems which utilize chilled water. Applications for this type of refrigeration include both process cooling and common air conditioning required for homes, commercial buildings, hospitals and manufacturing facilities. Water flash cooling vacuum vapor refrigeration systems do not use CFC (chlorofluorocarbons) refrigerants gases which damage the atmosphere or the dangerous ammonia and propane systems being proposed for larger systems. Air cycle refrigeration used on aircraft is too inefficient for home and commercial refrigeration.
At the time of filing of this patent there is much concern and activity in the refrigeration field as to which refrigerants gases will be used for replacement of the commonly used CFC's gases and CFC-11, CFC-12, in the present units and operating systems. Even the hydrochlorofluorocarbon, HCFC-22 series previously approved, environmentally are now in question. Major U.S. company has ceased manufacture of HCFC-22 equipment. The use of the expensive HCFC-123 and HFC-134A gases used in centrifugal compressor chilled water systems are in question. There are volumes of reports written on this crisis. In all cases none of these newly developed Halocarbon gases give cycle efficiency greater than the previously used CFC's. CFC refrigerants will not be produced after 1996 and manufacture is already severely reduced.
During the summer months the power used in the U.S.A. for refrigeration and air conditioning especially in commercial areas exceeds twenty five percent of the total energy utilized. Lower efficiency refrigeration systems should not be considered for this reason. It is noticeable that most American manufactures are attempting to adapt or fix their present equipment while Japanese have consortiums working to develop new types of refrigeration systems.
This patent is to introduce the proven thermodynamic principle of flashing water cooling vapor refrigeration. Water is undoubtedly the cheapest refrigerant known to man. This innovative system utilizes a unique type of vacuum vapor compressor to make the water vapor vacuum refrigeration systems applicable for air conditioning of homes, commercial establishments, and for industrial process refrigeration. Water vapor vacuum refrigeration at present is not in the state of the art for these applications, but is only used in large petrochemical and industrial applications. Only water or water glycol mixture is used as the refrigerant in the vapor vacuum refrigerant cycle.
The first historical objection to the water vapor vacuum refrigeration system has been the low operational vacuum range. This objection has now been overcome by progress in design, construction, seals and instrumentation. The second historical and most important objection is the large amount of flashed water vapor that the vacuum compressor must handle at the operating vacuum, with the low density gas and the high compression ratios required. The intent of this invention is to provide a new unique design features and a new type of compressor to overcome the objection of the large volume of vapor that must be compressed at the operating vacuum. High Pressure ratios of 4.75 to 5.75 are required for this system.
The only partially adaptable vacuum pump compressors for water vapor vacuum refrigeration units available today are the Roots type; however, they are not practical for small systems because they are slow, very large, heavy and expensive. Also at the required pressure ratio and flow requirements, an operational limit is reached on the Roots units due to mechanical clearances, heat generated and size requirements of the units. Other types positive or centrifugal compressors are too big and expensive.
Water vapor vacuum refrigeration is not new and is sometimes referred to as steam-jet refrigeration. This method utilizes multi-ejectors and are presently used where large volumes of waste steam at pressure normally from 50 PSIA to 100 PSIA, are available. For reference refer to ASHRAE 1983 Equipment Handbook, Chapter 13.1. The steam multi-ejectors are utilized to creative the low vacuum for water surface flashing in large, generally above 50 ton refrigeration capacity for the industrial and petrochemical industries. These units are huge and weigh tons and not for installation at homes, hospitals, small commercial business or industries. The theory of operation, however, is the same; to chill large quantities of water by flashing to temperatures 32.degree. F. to 45.degree. F. for distribution to areas for air conditioning or process cooling as in the present chilled water systems. The state of the art steam-jet system are open systems in that the chilled water is not recirculated. The coefficient of performance is low due to known inefficiencies of the multi-ejectors or steam-jets vacuum pumps.
The water vapor vacuum refrigeration unique system defined in this patent is a closed system with heat recuperation innovations resulting in a very high total overall thermal efficiency. The system is designed with a unique new type vapor compressor that will enable this system to be applicable to homes, hospitals, commercial air conditioning and industrial refrigeration requirements and process cooling. Units may be designed for load capacities as low as 3.5 tons to an approximate limit of 65 tons per unit with dual units of 130 tons of refrigeration capacity possible. Efficiency and coefficient of performance, COP, of the unique system is much higher than the present large and small Freon, CFC system thus saving much energy.